In the present work, porous gelatin scaffolds were prepared by cryogenic treatment of a chemically cross-linkedgelatin hydrogel, followed by removal of the ice crystals formed through lyophilization. This technique oftenleads to porous gels with a less porous skin. A simple method has been developed to solve this problem. Thepresent study demonstrates that the hydrogel pore size decreased with an increasing gelatin concentration andwith an increasing cooling rate of the gelatin hydrogel. Variation of the cryogenic parameters applied also enabledus to develop scaffolds with different pore morphologies (spherical versus transversal channel-like pores). In ouropinion, this is the first paper in which temperature gradients during controlled cryogenic treatment were appliedto induce a pore size gradient in gelatin hydrogels. With a newly designed cryo-unit, temperature gradients of 10and 30
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C were implemented during the freezing step, resulting in scaffolds with average pore diameters of,respectively, ±116 and ±330
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m. In both cases, the porosity and pore size decreased gradually through thescaffolds. Pore size and structure analysis of the matrices was accomplished through a combination ofmicrocomputed tomography using different software packages (
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CTanalySIS and Octopus), scanning electronmicroscopy analysis, and helium pycnometry.